WO2014053083A1

WO2014053083A1 - Process and device for production of compacted fertilizer charcoal

Info

Publication number: WO2014053083A1
Application number: PCT/CN2013/070128
Authority: WO
Inventors: Hans-Hermann Vennen; Ludger Wahrheit; Andreas Klumpe; Wilke Engelbart
Original assignee: Beijing Bht Environ Tech Co., Ltd
Priority date: 2012-10-06
Filing date: 2013-01-06
Publication date: 2014-04-10
Also published as: CN104781376A; CN104781376B

Abstract

Provided are a method of and an apparatus for thermo -chemical production of low-dust coal, shaped into pellets or other compacts, particularly from fertilizer-containing raw materials. The raw materials are partially burned with controlled air supply and thus charred; and the still glowing residues are quenched with water. The manufactured fertilizer-coal in this process largely retains its shape and can be used before the quenching in the still red-hot state similar like activated carbon for the treatment of exhaust gas in equipment.

Description

PROCESS AND DEVICE FOR PRODUCTION OF COMPACTED

FERTILIZER CHARCOAL

Field of the Invention

The invention relates to a method of and a device for the thermochemical production of coal using raw materials, which are compacted to pellets or other pressings, and which contain inorganic fertilizers.

Background of the Invention

It is desirable to use fertilizer-containing raw materials such as sludge from wastewater treatment plants (WWTP's), manure and dung from livestock enterprises, biogas plant residuals (digestate), so-called energy crops, wood or peat in processes, which offer a maximum of benefits for other tasks, especially for recovery of energy and re-use of the fertilizer.

A known process is the drying and burning of wastes. In doing so using known kilns, malfunctions happen by the formation of dust and/or by partial slagging of the ash. This results at least in an increased maintenance effort and in problems concerning the use of the ash, so that the efficiency of the whole is decreased.

The Indians in the Amazon already knew the beneficial effect of charcoal for the fertility of the soil more than 2000 years ago ("terra preta"). Since the last century, there are many attempts to use the "terra preta" effects with artificially made carbon. Fertilizer charcoal additionally to the soil-improving effect could bring a relatively large proportion of the carbon, which is absorbed by plants, for a quite long period back into the soil. What a high worth is connected with so-called biochar, was for example demonstrated in the 2nd Asia Pacific Biochar Conference, 2011. Because in the European Union the term "bio" may only be used when the conditions for a bio- certification are met, in the description of the present invention the more general names "fertilizer-charcoal" or "fertilizer-coal" are used.

Processes for the preparation of charcoal, so indirectly also for the production of fertilizer- charcoal, are well known. There are a lot proposed processes for the production of coal and charcoal from wood, wood waste, straw, green waste, from so-called energy crops, but also from wastes of various kinds, such as manure from animal housing, sewage sludge, residuals from biogas-fermenters, and peat. The raw materials are treated without oxygen supply at high temperatures, in doing so the organic (carbon-based) materials are thermo-chemically implemented into carbon, so charred. The resulting gases can be used in a downstream gas burner or for other purposes.

The energy output of all these charring processes is low, due to the calorific value of the resulting carbon, especially when using raw materials with a high mineral content. Processes for making coal, therefore, are mainly used only for a use of activated coal or for burning the coal. If wanted to gain more energy from the available raw material - as it is desirable in a wastewater treatment plant or in an animal farm - a second kiln is necessary.

For example, a "device for energy recovery from biomass and combustible waste, especially from renewable resources, as well as for carbonation" is proposed in DE 20 2011 001 453 Ul . At the output of this kiln is a heat exchanger to cool the produced coal indirectly. This plant should improve the energy efficiency; the heat exchanger is used to heat water for a use outside the plant. As "biomass" raw materials with a high caloric value and crushed to less than 40 mm particles are proposed. The materials should be thermo-chemically implemented into a coal having a high calorific value. This proposed device should be used only for a conventional carbonization process and for dust-containing materials; it works without air supply and therefore has a low energy yield. For further use of the produced coal a downstream burning system is proposed.

Because the caloric value of sludge from WWTP's is not high enough, a mere charring of WWTP-sludge is economically hardly possible. Similar conditions count for residuals of animal farms. The coal, which is produced in conventional charring, normally is rich in dust; this additionally causes a number of drawbacks when using the coal in downstream burning processes or when distributing the coal on agricultural fields. Dust of any kind can also be very harmful to the environment.

To avoid these drawbacks of methods of the prior art, a mixing of dusty coal with other materials and a subsequent treatment was proposed; but this extra treatment considerably reduces the profitability of the total process. A proposed subsequent production of pellets from coal dust using bitumen or other substances is costly; and it causes difficulties concerning the admission as fertilizer in agriculture.

A production of fertilizer-coal in the form of pellets or other compacts, with more energy yield than is possible with pure charring processes, is so far not succeeded in an economical and environmentally friendly way. There are only the mentioned solid-furnaces, which burn said materials to ashes.

Brief Description of the Drawings

Fig. 1 is the process and device for production of compacted fertilizer charcoal.

Detailed Description of the Invention

Initial object of the present invention was the improvement of the combustion of organic matter from agricultural farms with the aim to minimize the drawbacks of the known processes, which are caused by dust and slag.

In one of the experiments with a control (limiting) of the air supply, the combustion of the loaded pellets in a kiln, equipped with a rotary plate, was incomplete. Still glowing material, which smoldered in the ash-collecting vessel, came out of the kiln. When dousing with water, it turned out that this "ash" essentially consisted of pellets, which had high carbon content. This observation was very surprising, because in general it is expected that the material becomes decomposed during combustion.

This observation broadened the object of the present invention: Now measures should be provided for the production of as dust-free as possible fertilizer-coal. In doing this, the energy yield from the used raw material should be higher than in a pure charring process.

According to the invention this is achieved with a process in which materials, which are pressed to pellets or other compacts, are treated in a thermo-chemical converter with regulated air or oxygen-supply at less than 800 ° C, preferably at 400 to 700 ° C, so that the desired partial combustion- degree emerges, and wherein the compacted materials are moved in the converter with slowly running spiral conveyors, blades, rotating plates, sliding bottoms or like this to minimize abrasion. Crucial for maintaining the compacted form of the material is a quenching of the still glowing material with water or with water- containing mixtures at the end of the thermochemical converter or after leaving it and before exposure to air or to oxygen- containing gases.

This method according to the invention can be performed by means of a device for thermo-chemical conversion (converter, kiln, gasifier) that is equipped with a slowly moving screw, or with slowly turning shovels, a rotary plate, sliding bottom or like this, as well as with a device for the controlled supply of oxygen-containing gas, and with means for quenching the still glowing fertilizer-coal with the aid of water or with water-containing mixtures.

The inventive method prevents a detrimental formation of dust or slag. One can adjust the degree of combustion (the yield of energy with respect to the used material) in the process according to this invention by regulating the oxygen supply in such a way that the generated carbonaceous ash - the fertilizer-coal - has the desired higher or lower content of carbon. One can use the produced gas from the converter for combustion or for other purposes.

The quenching (dousing) according to this invention stops a prolonged burning of the only partially burned raw material. The steam, which is generated within the solid matter during quenching (dousing), additionally effects an improved generation of pores in the fertilizer-coal. The used compacts of the raw materials remain - despite partial combustion with air - surprisingly stable in shape. The produced compacted fertilizer-coal has about the same properties as activated carbon; this can be used for further embodiments of the invention.

Although, in this production of fertilizer coal one part of the original raw material, namely the resultant coal, is not utilized for energy production, this drawback is more than well compensated by the carbon content of the product: The fertilizer content in the fertilizer-coal is by binding to activated carbon significantly more valuable for agriculture and forestry than conventional fertilizers. Many materials, determining the fertilizer value, are protected from too rapid leaching in the soil by the micro porous carbon and the plants thus can sustainably use the fertilizers ("terra preta"). The other known benefits of activated carbon in the soil, increased water retention, increased humus formation, plant growth promotion, retention of pollutants, shall be noted here only briefly.

To improve the process of the invention for the production of more energy, raw materials with high fertilizer content (sewage sludge, manure, dung, excrement, digestate, etc.) preferably before compaction can be mixed with other materials with lower fertilizer content (dried green waste, dry energy-plants, wood, peat, etc.).

The invention is explained in detail with reference to a drawing below:

Fig.l shows a flow diagram with a thermochemical converter (kiln, solid-oven, gasifier) (10) with (not shown) slowly running spiral conveyors, blades, rotating plates, sliding bottoms or like this, with a feeder (1) for raw material, which is formed to pellets or other compacts, with a line (2) for supply of oxygen-containing gas, based on the temperature and/or on the oxygen concentration in the converter (10), and with a device (3) for the inventive quenching (dousing) of the produced fertilizer-coal with water or water- containing mixtures before exposing the product to oxygen-containing gas. In a simple embodiment it is useful to distribute water through a pipe (3) and (not shown) a nozzle on the fertilizer- coal into the outlet (4) of the converter (10) so that the glowing fertilizer-coal is quenched (doused) and will not continue to burn after leaving the converter (10). It is obvious that one uses the steam, which is generated during the quenching, for heating of drying air. The thermo- chemical converter (10) may be constructed perpendicular, such as (for example) a conventional solid-kiln with a division by (for example) a sliding bottom or a rotary plate into a heating chamber (12) and into a gasification space (11), or it may be constructed - different than shown here - horizontal or inclined like a rotary kiln or a tube with blades or with internal screw.

In a further embodiment, the glowing fertilizer-charcoal before an immediate quenching (dousing) can be used in a down-stream chamber (5), which is similar to a Hagenmaier drum, preferably at about 400 ° C, for the treatment of exhaust gas (21) of a gas burner (20), in which gases (13), which are formed in the converter (10) are burned. The treated hot gas can be discharged from the chamber (5) via a line (22) for a further use of the heat. After this pre-use of the fertilizer-coal for a treatment of exhaust gas in the chamber (5) the quenching (dousing) of the still glowing fertilizer-coal can be done via a water-line (31) in line or chamber (8). A further embodiment of the inventive method is shown for the use of exhaust air from a drying plant for raw materials (60) via a line (6) into the line (2). Another possibility for the use of the fertilizer-coal after quenching (dousing) for purification of exhaust gas (81) in a plant (80) of the stalls of a farm (82) is represented by line (8). Fertilizer- coal passes via lines (4 and / or 84) to storage (90).

The method of the invention - in combination with a drying equipment for the raw materials being processed, and / or in combination with a purification device for exhaust gases from burning the gases from the thermochemical converter, and also in combination with the purification of exhaust air from stables - provides a number of valuable additional improvements compared to conventional methods of charcoal production:

All inventive process steps are to be maintained with little effort and monitoring. They are economically applicable therefore not only in large commercial enterprises but also in a relatively small size, such as in agriculture farms.

By drying the original raw materials, by the simultaneously occurring disinfection, with a use of the oxygen-containing gases, which are pre-used for the drying of the original materials, during the inventive thermochemical production of fertilizer- coal a significant improvement of environmental hygiene on the farm is reached, because the possible spreading-out of disease and pests by conventional distribution of manure and slurry, unpleasant smells and not least the escape of dust and other pollutants are severely restricted by these measures.

For the drying of the original raw materials heat from the

thermochemical converter and / or from a downstream exhaust gas burner can be used.

After such a drying, raw materials from the agricultural farm can be environmentally friendly transported for mixing and pelletizing to large equipments, the pellets are brought back afterwards and are advantageously processed in conjunction with the drying plant in the thermochemical conversion plant to fertilizer-coal. Exhaust gas, condensates and waste heat of the drying system can advantageously be used in the production of fertilizer coal; the recovered surplus energy of the combined processes can be utilized in the agricultural farm, or for example, sold after generation of electrical power.

The partially to activated carbon converted raw material can be used for purification of exhaust gases from the combustion of the produced gases from the thermo- chemical conversion system, advantageously at about 400 ° C. Dioxins and furans, which are sometimes in exhaust gases are known to be largely removed in a so-called Hagen-maier drum. This purification can be done in a chamber, which also serves as a heat exchanger, or which is fed with cool exhaust gas.

Only after such an interim use the still glowing pellets need to be quenched (doused). This rapid cooling needs to be carried out only to such a temperature, which excludes a further burning in air.

By discharging the residual heat of the fertilizer containing carbon, which is still hot after quenching (dousing), in a cleaning system for exhaust of stables, for example in a chimney, the flow and the efficiency of the air purification system can be improved.

The raw materials, enhanced in the form of shaped fertilizer- coal, can economically be stored or marketed.

Distribution of the molded fertilizer- coal on soil can be done using conventional devices of agriculture and without pollution of the environment (dust, odor). The cost for this distribution compared with the cost for distribution of conventional fertilizer and manure are substantially reduced.

Overall, in this combined method of agriculture (forestry) and technology a significant amount of the carbon dioxide, taken from the atmosphere by the original plants, in the long term is conserved as soil carbon - like "terra preta".

Claims

1. Process for preparing shaped, low-dust fertilizer coal in a thermochemical conversion plant (10), which essentially consists of a known solid- incinerator and is equipped with slowly running circulating means for sparing abrasion, characterized in that the solid-incinerator is fed with pellets or with to other moulds compacted, low-dust raw materials, that air or oxygen-containing gas (2) is regulated supplied to the solid- incinerator (10) for an incomplete, partial combustion of the raw materials, and that a prolonged burning of the partially burned, still glowing material is stopped prior to further influx of air at least by quenching (dousing) with water or with water-containing mixtures.

2. The method of claim 1, characterized in that the still glowing material is used after leaving the thermochemical conversion plant (10) and before quenching (dousing) in a chamber or drum (5) for treatment of hot exhaust gas (21).

3. The method of claim 1 or 2, characterized in that the air or the oxygen- containing gas (2) contains gas (6) of a drying plant (60).

4. Apparatus for carrying out the method according to claims 1, 2 or 3, characterized in that the thermo- chemical conversion plant (10) consists of a solid- incinerator which is equipped with a feed line (1) for raw material compressed into pellets or other moulds, with slowly running circulating means for sparing abrasion, with regulation for the supplying air or oxygen-containing gas (2) and with at least one line (3) for the supply of water or of water- containing mixtures.

5. The apparatus of claim 4, characterized in that after the thermo- chemical conversion plant (10) and before of a supply of water or water-containing mixtures (31) there is a chamber or drum (5), through which hot exhaust gas (21) of a gas burner (20) is fed.